Effects of a Broad‐Spectrum Antibiotic on the Siberian Hamster (Phodopus sungorus ) Gut Microbiome

Abstract

The gut microbiome is a diverse, host unique, and symbiotic bacterial environment. Host antibiotic treatment can adversely affect the diversity of the bacterial population and the symbiotic relationship with the host. Although therapeutically beneficial, antibiotics can change the structure, function, and evolution of host microbial communities in the gut, affecting nutrient availability and predisposing infection in the gut by non‐communal species (Archie & Theis, 2011). Previous studies have shown the effects of antibiotics on the host's gut microbiome in many model species, including mice and rats (reviewed in Clarke, O'Mahony, Dinan, & Cryan, 2014), yet, in non‐model species, such as the Siberian hamster, the role of the microbiome and the effects that antibiotics have on gut microbial communities have yet to be fully explored. Studying non‐model species is particularly valuable because it enables us to make meaningful comparisons between various organisms and to understand the strategies they use to cope with environmental pressures. In order to study the various effects of antibiotics on the microbiome and ultimately the consequences it has on behavior in our species, we first had to determine if and how antibiotic treatment affects the gut microbiome of both male and female Siberian hamsters. In order to assess this question, male (n=12) and female (n=12) hamsters were either administered sterilized water or a broad‐spectrum antibiotic (0.3 μl of enrofloxacin (Baytril) 10% oral solution per gram of body mass) via sterile pipette orally once daily for seven days (Romick‐Rosendale et al., 2009). Body mass was monitored, and fecal samples were taken throughout the seven days before treatment (D1–7), the seven days during treatment (D8–14), and the seven days following the treatment period (D15–21). Microbiome analysis was completed to determine the effects of this broad‐spectrum antibiotic on the gut microbiome. At the end of the experiment, all animals were euthanized and organs were harvested and weighed. To determine the bacteria makeup of the gut microbiome, DNA was extracted and purified from the fecal material, and the V4 region of the 16S rRNA gene was amplified using the Illumina MiSeq platform to identify the bacteria present in each sample. Antibiotic treatment decreased the diversity of the microbial communities, and by the end of the recovery period (D21), the host gut microbiome was able to regain much of its microbial diversity. There were no significant differences in body mass, and additionally, the liver, spleen, and reproductive organs showed no significant difference in mass at the end of the study. The results of this work help us to advance our understanding of the gut microbiome's function in host communities, and they will allow us to further investigate the role that the microbiome plays in the gut‐brain axis in non‐model species.